ABAQUS simulation of a concrete plate under a temperature field and gravity 1

[hangv]

Question Background:
I have simulated the behavior of a concrete plate placed on a base, with ABAQUS. The interaction and concrete and base is 'hard contact' and separation is allowed. A friction of 0.15 is set between plate and base. In step 'initial', the temperature is 0 at both top and bottom surfaces of plate. In step 'apply load', the temperature remains 0 at bottom surface while that drops to -20 at top. The plate also undergoes the gravity force. The 'Mass Density' of plate is 200. The result is shown in the following picture.

Question:
When I change 'Mass Density' of concrete from 200 to 100 or smaller, I cannot get converged result, but a error message "Too many attempts made for this increment." But it is always OK for 'Mass Density' of 200 or greater. I wish anyone good at ABAQUS can figure out what is the problem. How can I get a good result with a 'Mass Density' approaching 0? (The reason I want to reduce the 'Mass Density' is that I have a theoretical equation for the model disregarding Mass Density, which can be used to verify results of ABAQUS)

 

[Mustaine3]

You have no convergence. I assume the other movements are not limited and so you have a singular system. Add contact stabilization or soft spring and check what's happening then.

 

[sumitnandi15]

Friend,I want to use a element that has stiffness as well as friction between concrete and bar.so i use axial connectors.for d11 value in elastic property i use stiffness.coefficient of friction can also be given.but i am confused with internal contact force value.how to calculate it???.please help.and do we nee to channge the orientation of the axis by giving a 90 degree rotation about y axis so that the axis of the of connector gets aligned to x axis.??Actually the i am using the connector in vertical direction that means a y axis on global coordinate system.thats mean do we need to do that rotation with ref to global so that the vertical direction becomes x axis for connector??

 

[Shz713]

Your result should not be affected by changing density if your analysis type is general static, if you're using explicit/implicit then the inertia effects are considered and density comes to play. Set your initial increment to 0.0001, minimum to 1e-20, maximum to 0.001 and total number of iteration to 10000; also turn off NLgeom and report your progress.

Shoot for the Moon, even if U miss, U still land among Stars!

 

[sumitnandi15]

i have a question. if i want to do the same model as hangv has done..will i use abaqua standard or explicit?.i also have to release the weight of concrete slab.and the temperature conditions to slab surface are to be applied in coupled temperature displacement step i assume?please reply

 

[Shz713]

We usually prefer displacement-controlled, try to stick we implicit unless ur analysis has motion (some sort of acceleration) in which u need to consider the inertia effect so go for explicit.
What u mean release the weight if slab? If ur trying to mimic an experiment do what has been done in the laboratory; else do a parametric study if u don;t have experimental data to see what would be the output when you have temp and dead load together and separately.

Shoot for the Moon, even if U miss, U still land among Stars!

 

[sumitnandi15]

yes i want the dead load of the slab to apply on the layers below.so will i use a coupled temp displacement step and use gravity as load for applying the dead load?

 

[sumitnandi15]

Actually i am not getting this displacement controlled thing?can you explain.is it a step of analysis?

 

[sumitnandi15]

previously u said that for density effect we have to use explicit.my slab has some density and i want to use it as dead load.so i am asking whether to use an explicit or we can use abaqus standard and put it in coupled temp dsplacement step?

 

[Shz713]

displacement controlled means you define a deflection at particular part of the structure for predefined period, then at the end of analysis you get to know how much force is required to reach such displacement (check youtube there are heaps of videos).

I said if ur analysis has inertia effect then u need explicit. Of course to let Abaqus work out DL u need to provide density of materials which can be done via static general. It seems you're not familiar with the objective of your analysis; I strongly recommend you read the documentation and exactly specify what you're looking for. For now, forget about explicit as your analysis can be done via implicit.

Shoot for the Moon, even if U miss, U still land among Stars!

 

[sumitnandi15]

hi shz713..i am new to abaqus and trying to learn by myself so having these difficulties.I tried with abaqus standard but it not considering the effect of gravity load or dead load in analysis.i think the acceleration value of 9.81 in component 2 of it is nottaken care of by standard.maybe explicit can help